JPH1020612A - Color image forming device - Google Patents

Abstract

PROBLEM TO BE SOLVED: To provide a color image forming device which is made compact by efficiently utilizing space and rationalizing layout, made well-balanced, and forms an image having no color slurring by facilitating alignment and performing registering. SOLUTION: Four sets of image forming units 20 equipped with an electrifying means 22 and a cleaning means 25 around a photoreceptor drum 21 are arranged two by two on right and left sides with respect to a perpendicular passing the center of a drum-like transfer drum 10 around the drum 10. The diameter of the drum 21 is set to 15 to 60mm and the diameter of the drum 10 is set to 80 to 200mm. The number of the teeth of the gear of the drum 10 is the integral multiple of that of the gear of the drum 21.

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to an electrophotographic color image forming apparatus for forming a color image by superposing toner images formed on a plurality of image forming bodies.

[0002]

2. Description of the Related Art An electrophotographic color image forming apparatus includes:
Although various proposals have been made, a tandem system (a system using multiple photoconductors) that can process four colors simultaneously in parallel is promising as a color system that has a wide range of support in print speed and the information society in the future. Have been.

As one method of forming a multi-color image by the tandem method, a plurality of image forming units in which developing means and image exposing means are arranged around an image forming body are arranged in parallel in a horizontal direction. There is a color image forming apparatus that forms a color image by superimposing a single-color toner image formed on each image forming body on a belt-shaped transfer body.

[0004]

In the above-described color image forming apparatus, (1) since a plurality of image forming units are arranged in parallel in the horizontal direction, the length becomes longer in the horizontal direction. There is a drawback that it is easily affected by distortion and thermal deformation and alignment is difficult, and (3) it is difficult to convey and align because it is superposed on a belt-shaped transfer member.

Therefore, the present invention is compact (first object), well-balanced (second object), facilitates alignment, matches resists, and has no color shift by streamlining the space and rationalizing the layout. It is an object to provide a color image forming apparatus capable of forming an image (third object).

[0006]

Means for Solving the Problems (First Invention) The first object is to provide a developing means around an image forming body and form a toner image on the image forming body.
A set of image forming units and the four sets of image forming units are disposed around the holding unit, and the transfer unit holds the transfer material, transfers the toner image on the image forming body onto the transfer material, and overlaps the toner images. And a transfer means, wherein the transfer means is in a drum shape, and the image forming bodies are respectively two right and left with respect to a vertical line passing through the center of the transfer means. The color image forming apparatus is characterized in that the four image forming units are arranged around the transfer unit.

[0007] The supply position of the transfer material supplied onto the transfer means and the separation position of the transfer material separated from the transfer means are set around the transfer means and near the vertical line. Further, the supply position is within a range of 25 ° ± 20 ° with respect to the vertical line, and the separation position is on the opposite side of the supply position with respect to the vertical line and 25 ° ± 20 °. 20 °, or the position where the image forming body of each of the four image forming units and the transfer unit contact each other is 4 ° with respect to the vertical line.
5 ° ± 20 °, 45 ° ± 20 °, 120 ° ± 20 °, 1
By being within the range of 20 ° ± 20 °, the respective image forming units are radially and isotropically arranged, so that the balance is maintained, the load applied to the transfer drum is made uniform, and the rotation is stabilized. In addition, it is less susceptible to distortion and thermal deformation, and further improves the exchangeability of the unit.

(Second Invention) A second object of the present invention is to provide a developing device provided around the image forming body and forming four sets of image forming units for forming a toner image on the image forming body, and the four sets of image forming units. An image forming unit disposed around, holding a transfer material, transferring a toner image on the image forming body onto the transfer material, and superimposing a toner image; The diameter of the image forming body is 15 m
m to 60 mm, and the diameter of the transfer unit is 80 mm to 200 mm, and the diameter of the transfer unit is 3 to 8 times the diameter of the image forming body. Can be achieved by

(Third Invention) A third object of the present invention is to provide a developing device provided around an image forming member, and four image forming units for forming a toner image on the image forming member; An image forming unit disposed around, holding a transfer material, transferring a toner image on the image forming body onto the transfer material, and superimposing a toner image; The transfer unit and the image forming body each include a gear, and mesh with each other, and the number of gear teeth of the transfer unit is an integral multiple of the number of gear teeth of the image forming body; Further, the number of gear teeth of the transfer unit between the gear of the adjacent image forming body and the number of teeth of the gear of the image forming unit may be an integral multiple, and / or The image forming bodies are provided with respective gears and meshed with each other. A drive gear is meshed with the transfer means, and the number of gears of the image forming body, the number of gears of the transfer means, and the number of gears of the adjacent image forming body are equal to the number of teeth of the drive gear. In this case, the number of gear teeth of the transfer means is set to an integral multiple.

[0010]

DESCRIPTION OF THE PREFERRED EMBODIMENTS A first embodiment of a color image forming apparatus according to the present invention will be described first with reference to FIGS. FIG. 1 is a sectional view of a color image forming apparatus showing an embodiment of the present invention, FIG. 2 is a sectional view of an image forming unit, and FIG. 3 shows a transfer drum and an image forming unit. It is a perspective view.

The transfer means 10 holds a transfer paper P as a transfer material on its peripheral surface, and forms a yellow (Y) formed by four image forming units 20Y, 20M, 20C, and 20K disposed around the transfer paper P. ), Transfer paper P holding toner images of magenta (M), cyan (C), and black (K)
The color toner image is formed by sequentially superimposing and transferring the image on the upper surface. The transfer means 10 is a drum-shaped transfer drum 10 and an aluminum base 11 which is a cylindrical metal base.
On top of this, a conductive rubber layer 12 (thickness of 500 to 5) is formed as an elastic layer.
000Myuemu, a urethane rubber layer) of the electrical resistance 10 ⁸ ~10 ¹¹ Ω · cm, as further releasing film 13 (for separation thereon, thickness 20 to 200 [mu] m, the electric resistance 10 ¹⁰ -
10 ¹⁶ Ω · cm Teflon layer). Further, the transfer drum 10 is provided with a gripper 14 which can be shifted as shown by an arrow and grips the leading end of the transfer paper P supplied from a timing roller pair r2 which is a supply means described later.

Around the transfer drum 10, there are provided a suction means 17 and a separation means 18. The suction roller 17 serving as a suction means is a means for bringing the transfer paper P, the tip of which is gripped by the gripper 14, into close contact with the transfer drum 10. The suction roller 17 is driven to rotate with respect to the transfer drum 10 as shown by an arrow, and presses the transfer paper P, whose leading end is moved with the rotation of the transfer drum 10, against the transfer drum 10, It is brought into close contact with the transfer drum 10 electrostatically. The separation claw 18 serving as a separation unit is a unit that separates the held transfer paper P from the transfer drum 10. The separation claw 18 is provided so as to be able to contact and separate from the transfer drum 10 as shown by an arrow, and comes into sliding contact with the transfer drum 10 only when the transfer paper P is separated.

The transfer drum 10 is supported on a front and rear panel (not shown) by a bearing (not shown), and further has a rotating shaft of the transfer drum 10 extending to the outside of the rear panel. Is provided. The flywheel 10F includes a transfer drum 10
In order to smoothly rotate without vibration, inertia force is applied.

First, the flow of the transfer paper P as a transfer material will be described. The transfer paper P is stored in a paper feed cassette CA that is a transfer material storage unit. The transfer paper P is carried out of the paper feed cassette CA by the operation of the paper feed roller r1.
The transfer paper P is fed to a timing roller pair r2 which is a supply means for supplying the transfer paper P to the transfer drum 10. The timing roller pair r2 sends out the transfer paper P at a predetermined timing. The transfer paper P sent out by the timing roller pair r2 abuts on the transfer drum 10, and the leading end thereof is gripped by the gripper 14 of the transfer drum 10. When the leading end of the transfer paper P is gripped by the gripper 14, the transfer drum 10 rotates in the direction indicated by the arrow. The transfer paper P moves with the rotation of the transfer drum 10, and is electrostatically brought into close contact with the transfer drum 10 while being pressed against the transfer drum 10 by the contact roller 17 that is driven and rotated by the transfer drum 10,
The paper passes below the separation claw 18 that is separated from the transfer drum 10. Thereafter, image forming units 20Y and 20
M, 20C, 20K image forming bodies 21Y, 21M, 21
C, 21K, the toner images formed on the transfer paper P are sequentially transferred onto the transfer paper P held on the transfer drum 10, and the transfer paper P
The toner images are superposed on each other to form a color toner image. When the color toner image is formed, the gripper 14
Release of the transfer paper P by the
8 comes into sliding contact with the transfer drum 10. Then, the held transfer paper P is transferred to the transfer drum 1 by the action of the separation claw 18.
Then, the sheet is separated from the upper side and further conveyed to the fixing unit 40. In the fixing unit 40, the color toner image is heated and pressed by the heating roller 41 and the pressure roller 42, and the color toner image is deposited and fixed on the transfer paper P.
3, the paper is discharged onto a paper discharge tray.

Next, the image forming units 20Y, 20M, 20C, and 20K arranged around the transfer drum 10
However, the image forming unit 20C has the same configuration except that the colors of the toner images to be formed are different from each other. Therefore, the image forming unit 20C will be described as an example.

The image forming unit 20C includes an image forming body charging means 22 around a photosensitive drum 21C as an image forming body.
C (hereinafter simply referred to as charging means 22C or charging device 22)
C), exposure means 2 such as an LED (light emitting diode)
3C, developing means 24C, image forming body cleaning means 25
C (hereinafter simply referred to as a cleaning means 25C or a cleaning blade 25C) is provided to form a cyan toner image on the photosensitive drum 21C.
When the image forming unit 20C is integrally detachable, it is preferable to integrate the photosensitive drum 21C, the charging unit 22C, and the cleaning unit 25C, or to add a developing unit 24C. Exposure means 23C
Is integrated according to the configuration.

Photosensitive drum 2 for forming cyan toner image
1C shows a photoconductive photosensitive layer provided on a cylindrical conductive substrate. At both ends of the photosensitive drum 21C,
In order to maintain the gap with the transfer drum 10, an abutting roller 211 </ b> C is provided coaxially with the photosensitive drum 21 </ b> C and is in contact with the transfer drum 10. Butt roller 211
In the contact portion 10T of the transfer drum 10 with which C contacts, the abutting roller 211C directly contacts the aluminum base 11 without providing the elastic layer 12. The transfer drum gear 10 of the transfer drum 10 is attached to one end of the photosensitive drum 21C.
A photoconductor gear 212C meshing with G is provided. As a result, the photosensitive drum 21C is positioned with respect to the transfer drum 10, and is driven to rotate in a direction following the transfer drum 10.

The charging means 22C is a means for applying a uniform electric potential to the photosensitive drum 21C. In the present embodiment, the charging means 22C is a roller-shaped roller charging roller which is driven and rotated while being in contact with the photosensitive drum 21C. The vessel 22C is used.

The exposure means 23C performs exposure based on an image signal (cyan) on the photosensitive drum 21C to which a uniform potential is applied by the roller charger 22C, and an electrostatic latent image corresponding to a cyan image. In the present embodiment, this is constituted by an LED in which light-emitting elements are arranged in an array in the axial direction of the photosensitive drum 21C and an imaging element (trade name: Selfoc lens). .

The developing means 24C is a means for containing a cyan toner as a developer, and reversal developing the electrostatic latent image formed on the photosensitive drum 21C to form a cyan toner image. In the developing unit 24C of the present embodiment, after the cyan toner accommodated in the developing unit 24C is stirred by the stirring member 241C, the surface of the toner supply roller 242C whose surface rotates in the direction indicated by the arrow is elastic (sponge). To supply to the developing sleeve 243C. At this time, the cyan toner on the developing sleeve 243C is made into a uniform thin layer by the thin layer forming member 244C. At the time of the developing operation of the developing means 24C, the developing sleeve 24 which rotates in the direction of the arrow is shown.
A developing bias to which DC or further AC is applied is applied to 3C, a jumping development is performed by one component contained in the developing means 24C, and a photosensitive drum 21C grounded has the same polarity as the toner. By applying a DC bias, non-contact reversal development is performed. Incidentally, the abutting rollers (not shown) provided at both ends of the developing sleeve 243C outside the image area come into contact with the photosensitive drum 21C, so that the developing sleeve 243C and the photosensitive drum 21C
And is kept in non-contact. In addition, instead of non-contact development,
Contact development can also be used.

The cyan toner image formed on the photosensitive drum 21C is positioned by the abutting rollers 212C, comes into contact with the transfer paper P held on the transfer drum 10, and has a polarity opposite to that of the toner. The image is sequentially transferred onto the transfer paper P by the transfer drum 10 to which a transfer bias voltage of 2 KV is applied.

The cleaning means 25C is a means for removing the cyan toner remaining on the photosensitive drum 21C from the photosensitive drum 10 after the cyan toner image has been transferred onto the transfer paper P, and is used in the present embodiment. In the form of
The residual toner is removed by the cleaning blade 25C slidingly contacting the photosensitive drum 21C.

Thus, the image forming unit 20C
Accordingly, the cyan toner image corresponding to the image signal (cyan) formed by the charging, exposing, and developing processes is transferred onto the transfer paper P held on the transfer drum 10.

Other image forming units 20Y, 20
Similarly, M and 20K are the photosensitive drums 21Y and 21K, respectively.
On the 1M and 21K, a yellow toner image corresponding to the image signal (yellow), a magenta toner image corresponding to the image signal (magenta), and a black toner image corresponding to the image signal (black) are synchronized in parallel processing. It is formed while taking. Then, each image forming unit 20Y, 20M, 20C, 20
The toner images formed on each of the photoconductor drums 21Y, 21M, 21C, and 21K of K are sequentially transferred to the transfer paper P held on the transfer drum 10 by the transfer drum 10 to which a transfer bias of 1 to 3 KV is applied. The image is transferred upward, and the toner images are superimposed. When all the toner images are superimposed, a color toner image is formed on the transfer paper P.

The transfer paper P on which the color toner image is formed is
As described above, the color toner image is separated from the transfer drum 10, is fixed, and is discharged onto the discharge tray.

On the other hand, the transfer drum 10 on which the color toner image has been transferred to the transfer paper P is
Is rubbed and cleaned on the transfer drum 10 by the fur brush 161. The fur brush 161 can be moved toward and away from the transfer drum 10 and slides on the transfer drum 10 when cleaning the transfer drum 10. The cleaning operation by the fur brush 161 may be performed while the transfer paper P is being separated for each print. However, the cleaning operation is performed intermittently before the transfer paper P is fed to the transfer drum 10 or after the transfer paper P is discharged from the transfer drum 10. It is preferable to perform the printing in such a way that the printing speed does not decrease due to the extra rotation.

Next, the first aspect of the present invention will be described with reference to FIG. 4, which is a view showing a main part of the above-described color image forming apparatus. 4 is a vertical line of the color image forming apparatus and a vertical line passing through the rotation center of the transfer drum 10.

In the present embodiment, the photosensitive drum 2
There are provided four image forming units 20 in which respective units for forming a toner image are integrated on one unit for four colors of yellow, magenta, cyan, and black. Since the four image forming units 20Y, 20M, 20C, and 20K are arranged two each on the left and right sides with respect to the vertical line, space efficiency is improved, and a rectangular isotropic appearance is achieved. And a compact color image forming apparatus can be obtained.

Further, the angles θ ₃ , θ ₄ , θ ₅ , θ ₆ from the vertical lines to the positions where the respective photosensitive drums 21 M, 21 C, 21 Y, 21 K and the transfer drum 10 are in contact are expressed by θ ₃ = Within the range of 45 ° ± 20 ° (25 ° ≦ θ ₃ ≦ 65 °) θ ₄ = Within the range of 45 ° ± 20 ° (25 ° ≦ θ ₄ ≦ 65 °) θ ₅ = Within the range of 120 ° ± 20 ° (100 ° ≦ θ ₅ ≦ 14
0 °) Within the range of θ ₆ = 120 ° ± 20 ° (100 ° ≦ θ ₆ ≦ 14
0 °), the image forming units 20 </ b> Y, 20 </ b> M, 20 </ b> C, and 20 </ b> K are arranged radially and isotropically with respect to the transfer drum 10. Therefore, the rotation can be stabilized and the exchangeability of the unit can be improved.

Also, θ ₅ −90 ° <θ ₃ , θ ₆ −90 ° <
By satisfying the condition of θ ₄ , it is easy to secure a space for holding and separating the transfer paper P.

In the present embodiment, the supply position of the transfer paper P supplied by the timing roller pair r2 (supply means) (the supply path of the transfer paper P indicated by the two-dot chain line intersects with the transfer drum 10). In this embodiment, the transfer paper P is separated from the transfer drum 10 by the separation claw 18 (the position where the leading end of the transfer paper P is gripped by the gripper 14). (The position in contact with the drum 10) is located near the vertical line, so that the image forming units 20Y, 20M, 20C, 20
Along with K, the load applied to the transfer drum 10 can be made uniform, and a small isotropic color image forming apparatus resistant to heat and deformation can be obtained. Further, the angle θ ₁ between the supply position and the vertical line is set within the range of θ ₁ = 25 ° ± 20 ° (0 ° <θ ₁ ≦
45 °), and the angle θ ₂ between the separation position and the vertical line is given by θ ₂ =
The angle is set so as to be within a range of 25 ° ± 20 ° (0 ° <θ ₂ ≦ 45 °).

As described above, in the present embodiment, since the units and means of the color image forming apparatus are radially and isotropically arranged with the drum-shaped transfer drum 10 as a center, the size can be reduced to a square. Further, a color image forming apparatus which is hardly subjected to distortion or thermal deformation can be provided.

In the second invention, each of the photosensitive drums 21Y, 21M, 21C,
By setting the diameter of 21K to 15 mm or more and 60 mm or less and the diameter of the transfer drum 10 to 80 mm or more and 200 mm or less, a compact image forming apparatus can be obtained without wasting space in the color image forming apparatus.

Further, each photosensitive drum 21Y, 21M,
By setting the diameter of the transfer drum 10 to 3 times or more and 8 times or less with respect to the diameters of 21C and 21K, each process unit can be arranged around the transfer drum 10 (lower limit), and furthermore, transfer is performed without creating an extra space. The size of the drum 10 can be reduced (upper limit).

Next, the third invention will be described with reference to FIG. 5 which is a schematic diagram showing the driving relationship. In FIG. 5,
212Y, 212M, 212C, and 212K are photoconductor gears for rotating integrally with the photoconductor drums 21Y, 21M, 21C, and 21K, respectively. The photoconductor gears 212Y, 212M, 212C, and 212K mesh with the transfer drum gear 10G of the transfer drum 10, and are driven to rotate by the rotation of the transfer drum 10. The transfer drum 10 meshes with a drive gear G that is driven and rotated by a drive source (not shown), and rotates following the rotation of the drive gear G.

Now, the number of teeth of the driving gear G is Z ₀ , the number of teeth of the transfer drum gear 10G is Z ₁ , and the photosensitive member gears 212Y, 212
The number of teeth of M, 212C, and 212K is Z ₂ (in the present embodiment, the photosensitive drums 21Y, 21M, 21C, and 21K).
K are all the same size, and the photosensitive member gears 212Y,
212M, 212C, and 212K have the same number of teeth, and are collectively referred to as a photoreceptor gear 212). Further, taking the photoreceptor gear 212C as an example, the photoreceptor gear 212C and the photosensitive gear adjacent to the photoreceptor gear 212C the number of teeth of the transfer drum gear between the body gear 212K and Z _3. Photoconductor gear 212
To the number of teeth Z ₂ of, and the number of teeth Z ₁ of the transfer drum gear 10G by an integer multiple _{(Z 1 = n 1 · Z} 2; however, n ₁ is an integer).
Further, with respect to the number of teeth Z ₂ of the photoconductor gear 212, and the number of teeth Z ₃ of the transfer drum gear 10G between the photoconductor gear 212 adjacent an integer multiple _{(Z 3 = n 2 · Z} 2; where, n ₂ is an integer). This facilitates the alignment, makes it possible to match the registration, and makes the color toner image formed on the transfer paper P an image without color shift.

On the other hand, with respect to the number of teeth Z ₀ of the driving gear G, the transfer drum gear teeth Z ₁ of 10G, the number of teeth Z ₂ of the photoconductor gear 212, the transfer drum gear 10G between the photoconductor gear 212 adjacent teeth Each number Z ₃ is an integral multiple (Z ₁ = n ₃ Z ₀ ,
Z ₂ = n ₄ Z ₀ , Z ₃ = n ₅ Z ₀ ; however, n ₃ , n ₄ and n ₅ are integers). Accordingly, even if driving unevenness occurs, the registration can be matched, and the color toner image formed on the transfer paper P is an image without color shift.

The photosensitive gear 212Y and the photosensitive gear 2
12M, the number of teeth of the transfer drum gear 10G is Z ′ ₃ ,
"When _3, Z _'3 (or, Z _3): Z" the number of teeth of the transfer drum gear 10G between the photoconductor gear 212M and the photosensitive element gear 212C Z ₃ = 1: 1 or 1: 2 to be Is preferred.

Although not shown, the number of gear teeth of the developing sleeve 243 and the number of teeth of the photosensitive gear 212 that couple (engage) with the photosensitive drum gear 212 in the image forming unit 20 are integers. By setting the ratio, it is possible to form a better image.

Next, a second embodiment will be described with reference to FIG. 6, which shows a main part of a color image forming apparatus.
In the above-described first embodiment, the transfer paper P is gripped by using the gripper 14, but in the present embodiment, the gripper 1 is held.
This uses a four-less transfer drum 10 '. Except for what is described below, since it is the same as the first embodiment, the same reference numerals are given and the description is omitted.

The transfer drum 10 'holds the transfer paper P on its peripheral surface, and is different from the structure of the metal layer / elastic layer in the transfer drum 10 of FIG.
For example, a configuration using PVdF (polyvinylidene fluoride) is used. At both ends of the transfer drum 10 ', which is a dielectric film, gears for holding the film and abutting and driving the photosensitive drum 21 as in FIG. 3 are integrally provided.

Inside the transfer drum 10 ', transfer corotrons 27Y, 27M, 27C, 27K and transfer baffles 28Y, 28M, 28C, 28K are arranged at positions facing the respective photosensitive drums 21Y, 21M, 21C, 21K. Has been established. This transfer corotron 27Y, 27M, 2
7C and 27K are the photosensitive drums 21Y, 21M and 21
C, a discharger for transferring the toner image formed on 21K onto transfer paper P held on transfer drum 10 'via a dielectric film. The transfer baffles 28Y, 28M, 28C, and 28K press the dielectric film from the inside of the transfer drum 10 'toward the photosensitive drum side when transferring the toner image, and transfer paper P and the photosensitive drum. 21Y, 21M, 21C and 21K are brought into close contact with each other.

At the position where the transfer paper P is supplied, an adsorbing corotron 151 is disposed inside the transfer drum 10 ', and an opposing roll 152 is provided on the peripheral surface of the transfer drum 10'.
Is disposed to face the adsorption corotron 151. The suction corotron 151 and the opposing roll 152 electrostatically attract the transfer paper P sent by the timing roller pair r2 onto the transfer drum 10 '. The opposing roll 152 is movable between a position where the transfer paper P is pressed and a retreat position as indicated by an arrow.

The separation corotrons 181 and 1 are located on the front side of the separation claw 18 with respect to the rotation direction of the transfer drum 10 ′.
82 are provided on the inner side and the peripheral side of the transfer drum 10 '. The peeling corotrons 181 and 182 are for applying a charge for peeling to the transfer paper P in order to remove the charge of the transfer paper P electrostatically held on the transfer drum 10 ′. The transfer paper P from which electric charges have been removed by the corotrons 181 and 182 is thereafter separated from the transfer drum 10 ′ by the separation claws 18.

Further, an inner static elimination corotron 191 and an outer static elimination corotron 192 are arranged on the inner side and the peripheral side of the transfer drum 10 ′ so as to face each other. The inner static elimination corotron 191 and the outer static elimination corotron 192 perform static elimination of the transfer drum 10 ′ from which the transfer material P has been peeled.

Here, the flow of the transfer paper P of the present embodiment will be described.

The transfer paper P sent at a predetermined timing by the pair of timing rollers r2 passes through a supply position between the opposing roll 152 sliding on the transfer drum 10 'and the transfer drum 10'. At this time, the transfer paper P
It is adsorbed on the transfer drum 10 ′ by the adsorption corotron 151 and pressed by the opposing roll 152. Thus, the transfer paper P is electrostatically attracted and held on the transfer drum 10 '. The transfer paper P held on the transfer drum 10 'is moved below the separation claw 18 and the fur brush 161 separated from the transfer drum 10' by the clockwise rotation of the transfer drum 10 'as shown by the arrow. And is conveyed toward the photosensitive drum 21Y. When the transfer paper P is held on the transfer drum 10 ', the opposing roll 15
2 retreats to a position separated from the transfer drum 10 '.

When the transfer paper P is transported to the position of the photosensitive drum 21Y, the yellow toner image formed on the photosensitive drum 21Y is transferred onto the transfer paper P by the action of the transfer corotron 27Y. At this time, the transfer baffle 28Y
Thereby, the photosensitive drum 21Y and the transfer paper P are in close contact with each other. Thereafter, similarly, the magenta toner image, the cyan toner image, and the black toner image are sequentially transferred, the toner images are superimposed, and a color toner image is formed on the transfer paper P.

Thereafter, the peeling corotrons 181 and 182 apply charges for peeling to the transfer paper P, and the separating claws 18 are brought into sliding contact with the transfer body 10 '. Therefore, the transfer paper P
Is removed from the transfer drum 10 ′ by the separation claw 18 in order from its tip after the charges are removed by the separation corotrons 181 and 182. The transfer paper P peeled off from the transfer drum 10 'is fixed with a color toner image by fixing means.

On the other hand, the transfer drum 1 from which the transfer paper P is separated
In step 07, static elimination is performed by the inner static elimination corotron 191 and the outer static elimination corotron 192 to prepare for the next image formation. Further, the cleaning operation by the fur brush 161 may be performed while the transfer paper P is separated for each print, but before the transfer paper P is fed to the transfer drum 10 ′ or after the transfer paper P is discharged from the transfer drum 10 ′. Intermittently,
This is preferable because the print speed does not decrease due to the extra rotation.

Also in this embodiment, the first
Similarly to the embodiment, the image forming units 20Y, 20M, 20C, and 20K are arranged at predetermined positions with respect to the transfer drum 10 '(first invention). The supply position and the separation position are set at predetermined positions. , The diameters of the transfer drum 10 'and the photosensitive drums 21Y, 21M, 21C, 21K (second invention), and the relationships between the drive gear G, the transfer drum gear 10G, and the photosensitive gear (third invention) ), The above-described effects can be obtained.

[0052]

As described in detail above, according to the present invention,
Four image forming units are arranged around the drum-shaped transfer drum so as to be two each on the left and right sides of the vertical line. And the process arrangement becomes compact (claim 1). In addition, since the image forming units are arranged radially and isotropically with respect to the transfer drum, the image forming units can be balanced, the load applied to the transfer drum can be made uniform, and the rotation can be stabilized. It is less susceptible to thermal deformation, and can further improve the exchangeability of the unit (claims 2 to 4).

Further, by defining the diameters of the transfer drum and the image forming body, the space in the color image forming apparatus can be arranged in a well-balanced process arrangement without wasting extra space without waste. , 6).

Further, by defining the gears to be driven, the alignment can be facilitated, the registration can be matched even if driving unevenness occurs, and the color toner image carried on the transfer drum can There can be no images (claims 7 to 9).

[Brief description of the drawings]

FIG. 1 is a sectional configuration diagram of a color image forming apparatus according to a first embodiment of the present invention.

FIG. 2 is a cross-sectional configuration diagram of an image forming unit.

FIG. 3 is a perspective view illustrating a transfer drum and an image forming unit.

FIG. 4 is a diagram illustrating a main part of the color image forming apparatus in FIG. 1;

FIG. 5 is a schematic diagram showing a driving relationship.

FIG. 6 is a diagram illustrating a main part of a color image forming apparatus according to a second embodiment.

[Explanation of symbols]

10 Transfer Drum (Transfer Unit) 20Y, 20M, 20C, 20K Image Forming Unit 21Y, 21M, 21C, 21K Photoconductor Drum (Image Former) 22Y, 22M, 22C, 22K Image Former Charging Means 24Y, 24M, 24C, 24K developing means 25Y, 25M, 25C, 25K image forming body cleaning means 18 separation claw (separation means) r2 timing roller pair (supply means)

Claims (9)

[Claims] An image forming unit provided with developing means around the image forming body, and a set of four image forming units for forming a toner image on the image forming body; Transferring means for transferring the toner image on the image forming body onto a transfer material and superimposing the toner image,
In the color image forming apparatus, the transfer unit has a drum shape, and the transfer unit is configured such that the number of the image forming bodies is two on each of right and left sides with respect to a vertical line passing through the center of the transfer unit. A color image forming apparatus, wherein the four image forming units are arranged around the means. 2. A supply position of a transfer material supplied onto the transfer means and a separation position of a transfer material separated from the transfer means are set around the transfer means and near the vertical line. 2. The color image forming apparatus according to claim 1, wherein: 3. The supply position is at 25 degrees with respect to the vertical line.
3. The method according to claim 2, wherein the separation position is within a range of ± 20 °, and the separation position is opposite to the supply position with respect to the vertical line and within a range of 25 ° ± 20 °. The color image forming apparatus according to the above. 4. A position where an image forming body of each of the four image forming units and the transfer means are in contact with the vertical line at 45 ° ± 20 °, 45 ° ± 20 °, and 120 ° ± 20 °, respectively.
The color image forming apparatus according to claim 1, wherein the angle is within a range of 20 ° and 120 ° ± 20 °. 5. A transfer material comprising: a developing unit provided around the image forming body; and four sets of image forming units for forming a toner image on the image forming body; And a transfer unit for transferring the toner image on the image forming body onto a transfer material and superimposing the toner image, wherein the diameter of the image forming body is 15 mm or more and 60 mm or more. Or less, and the diameter of the transfer means is 80 mm or more and 200 m or more.
m or less. 6. The color image forming apparatus according to claim 5, wherein the diameter of the transfer unit is at least three times and at most eight times the diameter of the image forming body. 7. A transfer material, comprising: a developing unit provided around the image forming body; and four sets of image forming units for forming a toner image on the image forming body; Transferring means for transferring the toner image on the image forming body onto a transfer material and superimposing the toner image,
In the color image forming apparatus, the transfer unit and the image forming body each include a gear, and mesh with each other, and the number of gear teeth of the transfer unit with respect to the number of gear teeth of the image forming body 2. The color image forming apparatus according to claim 1, wherein the number is an integral multiple. 8. The image forming apparatus according to claim 7, wherein the number of gear teeth of the transfer unit between the gear of the adjacent image forming body and the number of gear teeth of the adjacent image forming body is an integral multiple. Color image forming apparatus. 9. The transfer unit and the image forming body each include a gear, mesh with each other, and make the transfer unit mesh with a drive gear. 8. The apparatus according to claim 7, wherein the number of gear teeth of the body, the number of gear teeth of the transfer means, and the number of gear teeth of the transfer means between adjacent image forming body gears are each an integral multiple. Or a color image forming apparatus according to 8.